1. Technical Field of the Invention
The present invention relates generally to optical devices and more particularly to optimizations of optical devices.
2. Background Information
Optical devices, such as cameras and microscopes, use electromagnetic radiation to obtain information describing a target object. For example, a microscope may use electromagnetic radiation in the form of visible light to obtain an image of microscopic bacteria. The information obtained from an optical device describing a target object has an associated characteristic, referred to as resolution. The resolution defines the capacity of the optical device to resolve closely spaced features of the target object. The resolution of an optical device may depend upon a number of factors, including the inherent physical characteristics of the device and the wavelength of electromagnetic radiation used by the device.
An optical device may be used to produce an image of the target object. The image may comprise elements referred to as “pixels.” Each pixel is associated with a single value that represents a measured property on the surface of the target object. The measured property may include brightness, temperature, height, reflectivity, or any other meaningful characteristic of a surface. Typically, each pixel is associated with a specific surface area of the target object. The area is often referred to as the “footprint” of the pixel. The value associated with a particular pixel may represent the average of the measured property over the footprint of the pixel.
An array of pixels forms an image. The array of pixels is most often in a square or rectangular pattern, but other patterns (e.g., circular) may also be used. The imaged area of the target object is determined by the spacing and number of pixels in each of two, usually orthogonal, directions. The pixel spacing in a direction is the distance on the surface of the target object between the center points of two adjacent pixel footprints. The spacing may be different in the two, usually orthogonal, directions. The image length along one direction is given by the pixel spacing in that direction multiplied by the number of pixels in that direction.
Lateral resolution is a measure of how close two features on the surface of a target object may reside and still be distinguished in an image as two distinct features. Pixel spacing is often used as a rough indicator of the lateral resolution. Typically, two features must be separated by at least two times the pixel spacing. In some imaging systems, there may be additional constraints on the lateral resolution due to the overlapping of adjacent pixel footprints. When the additional constraints exist, the lateral resolution may be poorer than two times the pixel spacing.